Binders for modern coating systems are required to fulfil a multiplicity of requirements. Accordingly they must on the one hand exhibit certain technical coating properties such as scratch resistance, hiding power and weather resistance, while on the other hand good processing qualities, economical preparation, and the fulfilment of statutory impositions are to be ensured.
EP 0006517 describes siloxane-modified binders based on polyacrylate resins and polyesters for the production of coating materials. A disadvantage of the binders described therein is that at sufficiently low VOC levels (Volatile Organic Compound) they frequently no longer possess the desired profile of properties—for example, inadequate weather resistance and also chemical resistance.
EP 1247823 describes solvent-borne binders preparable by polymerization of a polyester component and an acrylate component. A disadvantage of the binders described therein is that owing to excessively high VOC levels it is impossible to realize eco-friendly coatings having a VOC content <250 g/L. Furthermore, binders of this kind with a solids content of more than 75 wt % cannot be prepared, owing to excessive viscosity.
It is an object of the present invention to provide improved binders which can be used in order to provide long-lasting coatings.
The complex object stated above is achieved by binders in accordance with the present invention.
A first subject of the present invention are binders based on a hydroxy-functional acrylate resin A), an alkoxy- and/or silanol-functional polysiloxane B), one or more dicarboxylic or polycarboxylic acids C) and one or more diols or polyols D), the constituents A) to D) being present condensed with one another in the binder.
The stated binders are obtainable by polycondensation of the above-stated constituents A) to D).